The story of this problem begins with the pioneering work from
Michel Caillaud (R3
Problemesis 1999), showing two white Ceriani-Frolkin Bishops and two black Pronkin Queens. It has
been followed by an improvement from
Silvio Baier (P0327 StrateGems 2012), showing one
more white Ceriani-Frolkin Bishop. Here is improved Michel’s entry the other way, by adding a third
black Pronkin Queen. This problem seems to be the very first one showing at the same time two
Ceriani-Frolkin pieces and three Pronkin pieces.
A further improvement would be to glue Michel's and Silvio's renditions in order to reach the combination
CF(B,B,B) & PR(q,q,q), but it looks extremely difficult. Another improvement possibility would be to get rid
of the visible Pronkin Queen, although it is not mandatory for such a piece to be captured. It also looks very complicated.